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final reportp Project code: AWW.0187 Prepared by: Dr Scott Norman1 Mr John Bertram2 Prof Michael McGowan3 1 Charles Sturt University 2 Qld Dept of Primary Industries and Fisheries 3 University of Queensland Date published: November 2008 ISBN: 9781741917420 PUBLISHED BY Meat & Livestock Australia Limited Locked Bag 991 NORTH SYDNEY NSW 2059 Prevalence of selected abnormalities in polled and horned bulls which affect breeding soundness Meat & Livestock Australia acknowledges the matching funds provided by the Australian Government to support the research and development detailed in this publication. This publication is published by Meat & Livestock Australia Limited ABN 39 081 678 364 (MLA). Care is taken to ensure the accuracy of the information contained in this publication. However MLA cannot accept responsibility for the accuracy or completeness of the information or opinions contained in the publication. You should make your own enquiries before making decisions concerning your interests. Reproduction in whole or in part of this publication is prohibited without prior written consent of MLA. Breeding Soundness Abnormalities in Polled and Horned Bulls Abstract The major objective of this project was to evaluate the evidence of reported associations between specific abnormalities affecting bull breeding soundness (preputial prolapse, reduced serving capacity and premature spiral deviation of the penis (PSDP) and the polled condition. The systematic review of published scientific literature and industry anecdote concluded that factors not likely to be related to the polled condition, such as sheath structure, probably have a greater influence on the occurrence of preputial prolapse than any negative effect of the polled condition. No evidence was found of a relationship between the polled condition and reduced serving capacity or libido. The systematic review found that PSDP was likely to be heritable, but there was no evidence it was directly associated with the polled condition. Analysis of serving ability/capacity data from bull breeding soundness data bases provided by 3 veterinary practices and 2 beef cattle researchers confirmed previous reports that the prevalence of PSPD increases with age, being markedly greater in bulls ≥ 3 years of age. For bulls ≥3 years of age approximately twice as many cases of PSPD were detected in polled-breed bulls (13.5%; n=496) than in horned-breed bulls (5.6%; n=233), clearly indicating that it is a much greater problem in polled-breed bulls but occurs frequently enough in horned-breed bulls to suggest that it is unlikely to be simply associated with the polled gene. With the likely greater use of polled-breed bulls in beef herds, producers of polled-breed bulls should be encouraged to conduct serving capacity tests on their ≥ 3-year old herd sires to identify those affected with PSPD. Further, with the support of relevant breed societies and geneticists, strategies which may include the use of DNA marker technology should be established to enable seedstock producers to select against this problem. Page 2 of 46 pages Breeding Soundness Abnormalities in Polled and Horned Bulls Executive Summary The MLA funded project AHW.094, ‘Genetic options to replace dehorning of beef cattle in Australia’ found there were potential associations between the polled condition and abnormalities affecting the breeding soundness of bulls. The researcher recommended that these possible associations be further investigated to define the potential magnitude of the problem. The current project consisted of two parts: Part 1: A systematic review was conducted of published scientific literature, reports from breed societies in Australia and elsewhere in the world, and unpublished studies and reports from researchers and reproductive specialists on the occurrence of breeding soundness abnormalities in polled and horned bulls. Three conditions affecting bull fertility have been implicated as being associated with the polled condition. These are preputial prolapse, reduced serving capacity, and premature spiral deviation of the penis (PSDP). Part 2: Retropsective analysis of the findings of serving ability/capacity testing derived from BBSE data bases provided by 3 veterinary practices (north-west and central NSW, southern WA) and 2 beef cattle reproduction researchers (WA and Qld) was conducted to determine the prevalence of PSPD by breed, age and breed-horn status. Based on the findings of Part 1 the association between preputial prolapse and the polled condition in bulls may be summarised as follows: 1. The polled condition is almost certainly associated with a higher prevalence of reduced size, or absence of the caudal preputial muscle. Reduced, or absent caudal preputial muscles seem to be associated with an increased prevalence of preputial eversion. 2. There is no scientific evidence that an increased prevalence of preputial eversion is related to an increased prevalence of preputial prolapse in Bos taurus breeds. However, in some Bos indicus derived breeds there is some evidence to suggest that an increased prevalence of preputial eversion may be related to an increased prevalence of preputial prolapse, and the findings from one small study conducted in Queensland suggest that polled bulls may have an increased risk of preputial prolapse compared to horned bulls. 3. Bulls with poor sheath structure and a propensity for preputial eversion may be more at risk of preputial prolapse, and this conformational combination is more likely to occur in Bos indicus derived breeds. In contrast, a bull with good sheath structure (as is more likely with Bos taurus breeds) and a propensity to evert has minimal risk of preputial prolapse. That is, sheath structure may be the pivotal trait determining the occurrence of preputial prolapse, with reduced function of the caudal preputial muscles and preputial eversion being significant only if associated with poor sheath structure. 4. Dissemination of the poll gene is unlikely to significantly increase the prevalence of this preputial prolapse. Sheath scoring systems are available (Breedplan and Australian Cattle Veterinarians) which could be used to assist producers with the selection of bulls with satisfactory sheath structure. The heritability of sheath structure is considered to be moderate. 5. Further, there appears to be no evidence implicating a relationship between the polled condition and reduced serving capacity or libido, and except for PSPD no other conditions affecting bull fertility that could be directly related to the polled condition were identified. Page 3 of 46 pages Breeding Soundness Abnormalities in Polled and Horned Bulls Based on the findings of Parts 1 and 2 of this project, the association between PSDP and the polled condition in bulls may be summarised as follows: 1. Evidence of the association between these two traits is generally based on anecdote, or studies performed 23 to 50 years ago on relatively small numbers of animals (except one Australian study). Examination of the data in these studies indicates PSDP is more likely to be associated with breed and familial lines, in contrast to a specific association with the polled condition. Subsequent authors referring to these studies have perhaps erroneously concluded that the higher prevalence of PSDP in polled breeds implies a direct association with the poll gene. An Australian study of 1,000 B. taurus bulls found that 16% of polled-breed bulls had PSPD compared to 1% in horned-breed bulls. 2. PSPD was by far and away the most common abnormality affecting the serving ability/serving capacity of bulls detected by veterinarians and researchers in Part 2 of the project. It was rarely detected in young bulls (1- to 2-year olds) but across breeds 8.2% (n=939) of 3- to 6-year old and 18.4% (n=179) of >6-year old bulls were diagnosed with PSPD. For bulls ≥3-years of age approximately twice as many cases of PSPD were detected in polled-breed bulls (13.5%; n=496) compared to horned-breed bulls (5.6%; n=233), clearly indicating that it is a much greater problem in polled-breed bulls but occurs frequently enough in horned-breed bulls to suggest that it is unlikely to be simply associated with the polled gene. 3. From Part 2 of the project the overall prevalence of PSPD in polled-breed bulls (4.4%; n=2,431) was non-significantly greater (P=0.079) than in horned-breed bulls (1.5%; n=1,433). With the likely greater use of polled-breed bulls in beef herds, producers of polled-breed bulls should be encouraged to conduct serving capacity tests on their ≥ 3- year old herd sires to identify those affected with PSPD. Further, with the support of relevant breed societies and geneticists, strategies which may include the use of DNA marker technology should be established to enable seedstock producers to select against this problem. Page 4 of 46 pages Breeding Soundness Abnormalities in Polled and Horned Bulls Contents 1 Background .......................................................................................................... 7 2 Project Objectives................................................................................................ 8 3 Methodology......................................................................................................... 8 4 Part 1 - Review...................................................................................................... 9 4.1 Overview ..............................................................................................................